I love games like this! Have a massive soft spot in my heart for geometric art, and arcady games in game jams are my favorite!
I think you could have made the different obstacles appear much faster, maybe reduce the length of the first segment to 1/2 or maybe 1/3rd of it's duration, so people get to enjoy the variety of obstacles sooner.
When using rectangles for art one thing that is incredibly easy to implement in unity is 2d lighting, and more precisely 2d shadows. If you attach a light to the player and make all the obstacles cast shadows, the game looks significantly better with very little work from your end.
Another thing I'd add is a very simple animation to turn the cube 90degrees to the left when turning left, and 90 degrees to the right when turning right. You can look into doing it with unity's animation system, or just through code. It can make the whole game feel much more responsive when there are visual reactions to your input, and both of these are easy to implement!
Overall I enjoyed playing your game, I enjoy simple concepts executed simply. Well done!